New 3D tech addresses thermal runaway concerns

GERMAN company Freudenberg Sealing Technologies (FST) has launched customised three-dimensional (C3D) fire safety components for lithium-ion EV batteries.

The technology places thermal barriers inside the battery pack that help to slow down or even stop thermal runaway by increasing resistance to propagation.

The lightweight C3D thermal barriers can be used at various positions within the battery and have already proven reliable in their initial series productions.

FST says it is gearing up the technology to meet the demands of an expected 100-million-plus electric cars on roads across the globe by 2030, each bringing with the risk of thermal runaway due to manufacturers’ efforts to increase battery range and reduce recharging times.

The heat-resistant, electrical- and thermal insulating materials that have been tested in-house by FST are said to safely withstand temperatures of up to 1200°Celsius. The barriers are fabricated from extremely heat-resistant compounded polymers which are resistant against particle impacts, such as those that occur when cells are vented.

The C3D thermal barriers utilise elastomer solutions, whether in solid form or as a foam, as well as plastic components such as Quantix Ultra, (a new class of plastic materials that neither melt nor catch fire at very high temperatures) which enables complex geometries.

“What is completely new is that the thermal barriers are now also available in customised, flexible 3D geometries, which makes it possible to use them in various positions within the battery and allows for integration of additional components,” explained Freudenberg Sealing Technologies global vice president of technology, Andrew Espinoza.

Beyond the existing two-dimensional barriers, such as flat mats and thermal blankets, the C3D variant opens entirely new possibilities.

Mr Espinoza says customer-specific, lightweight 3D geometries can be produced in a variety of high and low volume manufacturing processes, such as injection moulding and continuous extrusion.

“Profile seals, module separators and covers, including those for bus bars, cooling lines or electrical components are a few of the products currently being produced,” he added.

“The 3D thermal barriers and the utilised materials have gone through extensive testing that exceeds the required standards. They have proven their outstanding performance and reliability on bench tests as well as battery system testing.

“The products meet the highest quality standards, are certified pursuant to UL 94 V-0 and are already being used successfully in initial series production for the automotive industry.”

With higher energy density, lithium-ion batteries have an increased risk of thermal runaway, which is the ignition or explosion of a battery cell caused by a self-reinforcing heating process.

It can be caused by a range of internal and external factors, such as overcharging, excessive discharging, damage, or heating of the battery and can release not only flames and hot gases but also electrically conductive particles.

These in turn can cause thermal propagation in adjacent cells and lead to short circuits in the electrical system.

The phenomenon is speculated to have been responsible for numerous EV carrying ship fires over the past decade and other lithium-ion battery using appliance fires including mobile phones and laptop computers.